Top Tips

There are many contributing factors that may lead to a landing incident/accident, but one that ATC can have a major influence on is the development of an unstable approach. In general terms, if an arriving aircraft is too high or too fast, the approach will most likely become unstable.

Runway Excursions

What is a Runway Excursion?

The Civil Air Navigation Services Organisation (CANSO) defines a runway excursion as "An event in which an aircraft veers off or overruns the runway surface during either take-off or landing." Runway excursions lead to more runway accidents than all the other causes combined.

What causes a Runway Excursion?

There are many factors that may cause a runway excursion, including runway contamination, adverse weather conditions, mechanical failure, pilot error and unstable approaches. This briefing will focus only on unstable approaches.

Establish Approaches

What is an Unstable Approach?

An unstable approach is simply an approach that does not meet the criteria for a stable approach established by the aircraft operator. As an illustration, Flight Safety Foundation defines a stable approach in the following terms:

On the correct flight path:

ILS Approach – ILS within 1 dot of the localizer and glide slope.

Visual Approach – Wings level at 500 feet AGL.

Circling Approach – Wings level at 300 feet AGL.

Only small heading and pitch changes required.

Speed within +20/-0 kts of reference speed.

Aircraft must be in proper landing configuration.

Maximum sink rate of 1,000' per minute.

Appropriate power settings applied.

Briefing and checklists complete.

During IMC – Stable by 1,000 feet AGL.

During VMC – Stable by 500 feet AGL.

If the approach is not stable by 1,000 feet AGL or 500 feet AGL (depending on weather conditions), or if the approach becomes unstable below these altitudes, the pilot should initiate a missed approach/go around. The pilot may initiate a go around at any time above or below these altitudes if deemed necessary. It is possible for a pilot to initiate a go around even after touchdown on the runway, but not after the thrust reversers have been deployed.

For ATC purposes, in the most basic terms, if an arriving aircraft is too high or too fast, the approach will most likely be an unstable one.

ATC Role

What Role does Air Traffic Control play?

ATC can influence the safety and stability of an approach in two general areas. First, the instructions and clearances that are issued to the pilot can be significant factors in determining if an approach will become unstable. For example, if a descent clearance is delayed and the aircraft is close-in to the runway, the aircraft may be high on the approach, leading to a flight profile that is both above the glide slope and at a high sink rate.

Second, ATC plays a critical role in providing information to the pilot. For example, if the surface winds suddenly shift from a headwind to a tailwind, the aircraft's flight profile may be significantly affected. If the wind information is promptly and accurately relayed to the pilot by ATC, the pilot would then be able to anticipate and compensate for the effects of the wind, making the necessary corrections to ensure a stable approach or request an alternate runway.

Avoid Unstable Approaches

ATC Best Practices to Avoid Unstable Approaches

A stable approach ends with the successful completion of the landing and rollout. The stable approach may begin, however, 100 miles or more from the airport. En-route control and terminal approach control both play key roles during the initial descent phase and in positioning the aircraft on the final approach. The tower local control also has a very important role in determining the outcome of the approach and landing.

General ATC

Inform the pilot what to expect regarding runway assignment, type of approach and descent/speed restrictions so the proper planning and execution can be conducted. Stable approaches require predictability and planning. Avoid last minute changes unless absolutely necessary, and advise the pilot as early as possible when changes are anticipated.

Ensure the runway assignment is appropriate for the wind. Excessive tailwinds or crosswinds can lead to unstable approaches, and especially when the runway is wet or contaminated, are often associated with runway excursions.

Issue accurate and timely information related to weather conditions, wind and airport/runway conditions. When conditions are rapidly changing, promptly inform the pilot of all significant changes. Keep the overlying control facility (approach control or en-route) advised of changing conditions as well.

Apply appropriate speed control/restrictions. Assigning unrealistic or improper speeds, both fast and slow, or assigning speed control close-in to the runway may lead to unstable approaches.

Be responsive to pilot requests, especially those involving speed assignments, descent requests or runway/approach assignments. If you are unable to accommodate the pilot's request, advise the pilot of the reason, and if able, offer an alternative.

En Route & Approach

Avoid routine vectoring of aircraft off a published arrival procedure to shorten the flight path. Unexpected shortcuts may lead to insufficient time and distance remaining to maintain the desired descent profile, and causing the aircraft to be high on the approach. Avoid close-in turns to final.

When smaller aircraft are sequenced behind larger aircraft the pilot of the smaller aircraft may elect to stay above the glide slope in order to maintain wake turbulence separation from the larger aircraft. Controllers should be aware that this combined with an ATC higher speed instruction may lead to an unstable approach.

Avoid instructions that simultaneously combine a descent clearance and a speed reduction. Many aircraft are not capable of performing a simultaneous descent and speed reduction while maintaining a stable approach profile. Specify which action you expect to be performed first.

Issue appropriate and accurate track mile information from the airport or approach fix in a timely manner, as required.

Comply with requirements related to capturing the glide slope from below. Vectoring for an approach that places an aircraft on the final approach course above the glide slope is a leading cause of unstable approaches.

Tower

Avoid close-in, last second runway changes, even to a parallel runway. To comply with the company's operational procedures and requirements, the flight crew must have time to properly brief the approach and missed approach procedure to the runway being utilized. Even though a pilot may accept a runway change, the result may be an unstable approach.

Avoid pattern entry instructions that require the pilot to turn final close-in to the airport, especially with turbojet aircraft. For example, instructing an aircraft to enter on a close-in base leg may result in an unstable approach.

Issue timely weather information. When the surfaces winds are rapidly changing, ensure the pilot has the most current information. Solicit pilot reports on weather conditions and runway braking action and disseminate the information in a timely manner.

Be alert for signs of an unstable approach. For example, if an aircraft is above the glide slope altitude at the final approach fix, then an unstable approach is likely. When a possible unstable approach is detected, query the pilot and then be responsive to the pilot's requests.

Summary

Many factors can lead to an unstable approach, which in turn, may lead to a runway excursion. While a large number of these are beyond the control of ATC, controller involvement can play an important role in contributing to safe, stable approaches and reducing the risk of runway excursions. Recognising and identifying unstable approaches, issuing proper clearances and providing timely and accurate weather information are important actions that ATC can perform to significantly reduce the risk of runway excursions.

There are many contributing factors that may lead to a landing incident/accident, but one that ATC can have a major influence on is the development of an unstable approach. In general terms, if an arriving aircraft is too high or too fast, the approach will most likely become unstable.

Introduction Video

Allow the Arrival/Approach Procedure to be Flown as Published

If at all possible, minimize or avoid the use of vectoring.

Avoid Routine Vectoring

Avoid routine vectoring of aircraft off an arrival course to shorten the flight path. Unexpected shortcuts may lead to insufficient time and distance remaining to maintain the desired descent profile, and cause the aircraft to be high on the approach. Avoid close-in turns to final.

When Aircraft are Being Vectored, Issue Track Miles to the Airport

When aircraft are being vectored, issue track miles to the airport or approach fix in a timely manner, as appropriate.

Keep the Pilot Informed

Keep the pilot informed regarding runway assignment, type of approach and descent/speed restrictions. That will allow for proper planning and execution of the approach. Stable approaches require predictability and planning. Avoid last minute changes and advise the pilot as early as possible when changes are anticipated.

Ensure the Runway Assignment is Appropriate for the Wind

Wet or contaminated runways, combined with cross/tail winds are often associated with runway excursions.

Avoid Instructions That Combine a Descent Clearance and a Speed Reduction

Many aircraft can't descend and slow down simultaneously.

Comply With Operational Flight Requirements

Comply with operational flight requirements related to capturing the glide slope from below. Vectoring for an approach that places an aircraft on the final approach course above the glide slope is a leading cause of unstable approaches.

Avoid Close-In, Last Second Runway Changes

Avoid close-in, last second runway changes, even to a parallel runway. To comply with the company's operational procedures and requirements, the flight crew must have time to properly brief the approach and missed approach procedure to the runway being utilized. Even though a pilot may accept a runway change, the result may be an unstable approach.

Introduction Video

Maintain a Mental Picture of the Required Descent Profile

Advise ATC as Soon as Possible if Descent is Required or Additional Track Miles are Needed to Execute a Stable Approach

The sooner ATC knows, the greater is the probability that the request can be accommodated.

Be Aware of Published Local ATC Procedures/Airspace Restrictions that Impact the Approach

Airspace constraints may result in route and altitude restrictions.

Make Requests for Operational Requirements, Not for Convenience

The earlier you tell ATC the easier it is to accommodate any request.

Understand that you are part of a tightly integrated system with lots of arriving/departing aircraft and many operational variables (traffic patterns, airspace and airport design restrictions, noise restrictions, possible emergency operations on a different frequency), so ATC may not always be able to accommodate requests.

If You Can't Comply With an Instruction, Let ATC Know Early

Don't accept clearances that could put you into a situation leading to an unstable approach. The worst thing to do is to accept an instruction and then not comply with it.

Use extreme caution when accepting visual approaches at unfamiliar airports.

Be Predictable

As far as possible, minimize differences (ATC can't be aware of all the variables e.g. aircraft performance, airline SOPs, etc).

When Departing

Tell ATC if you're likely to need further time on the runway, before accepting a clearance to enter the runway. ATC might be making their plans for the arriving aircraft around you starting your take-off roll without delay.

If You Have an Emergency Situation

Let ATC know as soon as is practicable, either by selecting the appropriate Mode A or using the standard phraseology. Once ATC are aware of your situation, they will LEAVE YOU ALONE and can start making preparations to accommodate whatever YOU may request, when YOU are ready.

Introduction(0:46)

Max BiceManager of Safety ServicesAustralia

"For over 2 years, CANSO has been actively working with the aviation industry to improve runway safety. In a collaborative project, the CANSO safety and standard committees have created flyers for use by air traffic controllers and pilots on how to avoid unstable approaches and improve runway safety outcomes. These flyers are based on risk models that have been developed by controllers, pilots, airport operators, regulatory and safety specialists from around the world, through many workshops. They're easy to read and contain the key points to achieve stabilized approaches. After all, safety is a partnership between all members of the aviation industry. So let's work together to improve our runway safety performance."

Top Tips for Controllers(1:00)

Graham WadesonNATSUnited Kingdom

"An unstable approach can result from multiple causes. Some of which, as controllers we're not able to influence such as weather conditions. As controllers we can have a significant impact on the profile of the approach and therefore influence the likelihood of the approach becoming unstable. Which could, in turn, ultimately effect the safety of the flight. As controllers, our actions in the form of issuing clearances and passing information, can play a pivotal role in insuring that the pilot has the best opportunity of flying the required profile to establish and maintain a stable approach and therefore make a safe landing. Timely and accurate communications are a critical element and this is something that we do have control over and allows for the proper planning and execution of the approach. These top tips are pertinent for all controllers operating anywhere in the world, in any ATC environment, and will help us insure that safety remains at the forefront of every operation."

Top Tips for Pilots(0:47)

Fermín León GonzálezCaptain Aeromexico ConnectMexico

"A stabilized approach is very important for the conclusion of every flight. As an airline pilot we fly between 2 up to 6 approach and landings in one day. So what we are looking for during instrument approach at 1000 feet, and visual approach conditions at 500 feet AGL, you are on the right track the right path and the right speed with the airplane in landing configuration and the checklist complete. If not a missed approach go-around procedure must be accomplished. So we need to anticipate so we can have a safe landing."

Let ATC Know Early(0:30)

Yousef Al-AghwaniTower ControllerJordan

"Please communicate with me early if you have an issue. It is OK to say 'Unable' to my instructions. Please let me know what you need from the cockpit perspective and we as the controllers at Amman/Queen Alia tower will do our best to make the pattern work for all. It is really teamwork and we need to communicate as early as possible, in order to make sure you land safe."

Pilot's View of Runway Excursions(1:02)

Rory KayCaptain 757/767United Kingdom

"If we get to that final point in the approach, which is generally 5 hundred feet above ground level, so that's about 2...2 and a half miles out on the approach. If we don't have all those boxes checked off about our configuration, our speed, our horizontal, our vertical deviation is locked on, we are absolutely on the centerline, we're going to have to abandon that approach. That's called a go around. We know what a go around is, we don't like to perform them. Controllers don't like us to perform them. The passengers don't like us to perform them. It is a lose lose situation. It is a much higher work load for the pilots. A higher workload for the controllers because they have to take us around and fit us back into what may be a very busy stream of arriving traffic already. And to be frank, it can be an alarming maneuver for a passenger to experience in the back of a plane. The closer into the runway that we execute a missed approach or go around the more alarming the maneuver can feel to some who are not used to such things."

CANSO is Fully Committed(1:15)

David HarrisonDirector of Safety, NATSUnited Kingdom

"CANSO is fully committed to maintaining and improving aviation safety. A lot of work has already been undertaken, but there is still much more we can all do in the prevention of runway excursions. Despite all of our efforts, there are still on average 2 runway excursions globally every week. With unstable approaches being a causal factor in many of these. CANSO is working in close collaboration with our ATM industry partners. Airlines, pilots, airports and regulators to address the causes, but the role air traffic control plays can be crucial in determining the safety of a flight. We need to insure that the service provided by ATC is conducive to safe and effecting flight. Providing pilots with the instructions, clearances and information that enable them to take the appropriate actions and decisions from cruise through to final approach and landing. Aviation connects and effects all of us, allowing the global community to grow and prosper. People rely on ATC to be professional and proactive to enhance safety. Through working together as one safety team and acknowledging and understanding the part each of us play we can make a difference."

The Important Points(0:50)

Rory KayCaptain 757/767United Kingdom

"A stabilized approach is vitally important to the safe conclusion of a flight. It doesn't matter what the weather is. Whether it's sunny and good visibility, or a day like today where the visibility is simply awful. The important part about a safe approach is to have the aircraft at a particular point, at a distance out on the approach. Generally 3 to 5 miles, which is about 1,000 to 1,500 feet above ground level where we are in a safe position to land. The landing gear is down, the flaps are down in the landing position and horizontally and vertically exactly in the right place that we want to be and the speed is at the landing speed."

Controllers Play an Important Part(0:37)

Magnus TeoCAASSingapore

"Our controllers take the application of speed control seriously. They're always mindful if the aircraft speed is too fast or slow. We follow ICAO's recommendations, which basically means not restricting the aircraft's speed at 5 aeronautical miles or less from touchdown. Another consideration that controllers take before flight speed control is the wind speed and direction. If the head wind is strong, the aircraft might fly slower than normal and therefore we should adjust the speed control accordingly."

Corporate Jet Experience(0:47)

Kevin BachandCaptain G550/G450United States

"As a corporate pilot flying a business aircraft our destinations change day to day. We can be flying to very big airports, or very small airports. Some of the bigger airports with the long runways are served by a full instrument approach. Some of the smaller airports with the shorter runways may have no approach at all. During the last month I've been to the Mideast, South America, New England. On one particular trip, which was a 10 hour flight with a fuel stop at the 5 hour mark our first landing was on a 12,000 foot runway during the day time. 5 hours later after a total of 10 hours flying we're shooting approach of a 6,000 foot runway at night in the middle of a big city. In order to do this safely we need the opportunity from air traffic control to fly a stabilize approach."

Undesirable Aircraft State(0:35)

Brandon MillerRadar ControllerUnited States

"We want to make sure that the aircraft doesn't get into an undesirable aircraft state. And we want to make sure that the stabilized approach is a maximum goal between controllers and the air crew flying the airplane. We want to set the pilot up to be able to achieve the approach without an overrun possibility or the possibility of a go around. So we want to make sure we do everything together as soon as possible to achieve the stabilized approach all the way to the runway environment."

An Exercise in Energy Management(0:33)

Kevin BachandCaptain G550/G450United States

"Although a business aircraft is typically smaller than a large commercial aircraft, the challenges we face as pilots are still the same. We need to get the airplane from the initial approach fix down to the runway in a stabilized fashion. It's an exercise in energy management. Given the opportunity from air traffic control to fly a stabilize approach we can get the aircraft to the touch down zone at the proper air speed. Thereby eliminating the possibility of a runway excursion."

Approach Sequence(0:30)

Brandon MillerRadar ControllerUnited States

"As a radar controller my main focus is the approach sequence into the airport with multiple aircraft and I want to make sure I put the pilot in a situation where he's at the proper altitude and speed to achieve a stabilized approach, starting from the final approach fix out. Safety being the number one goal, I want to make sure I do everything in my power to ensure that that pilot has the best fighting chance of a stable approach to the runway."

Air Speed is Critical(1:13)

Rory KayCaptain 757/767United Kingdom

"As an airline pilot, I want the controllers that we work with day in and day out to understand the importance of having my airplane configured at the right place, at the right speed. The speed control is absolutely critical. We are used to flying the initial parts of an approach quite fast, maybe at 190 or 200 knots. But as we start down, it's important for a controller to understand we need to meet the gates that I've already discussed and we need to be on speed. It's not just a physical location issue. Slowing a swept wing jetliner down, as it descends on a glideslope, is quite difficult. So the sooner we can get that speed under control at a target speed we are confortable with, even before we start down, is very desirable. The bigger that plane the harder it is to slow as it goes down that glideslope. Therefore, I want the controllers to understand just how hard our workload is if they require us to maintain a very high speed until very close-in to the airport. And that is reducing my chances of executing a stabilized approach and increasing my chances that I may have to abandon it and come around and do it again."

Importance of Flying a Stabilized Approach(0:33)

Kevin BachandCaptain G550/G450United States

"What I want controllers to know is that although business aircraft are typical smaller and may be more maneuverable the importance of flying a stabilized approach in this type cannot be over emphasized. These aircraft have a tremendous amount of energy that needs to be dissipated on landing and roll out and because of this there no more immune to the hazardous of an unstabilized approach than is a large commercial aircraft. Additionally, an unstabilized approach must result in go around. Go arounds take time, fuel, money. They're unsettling for the passengers and they're an additional work load on the crew and air traffic controllers as well as they try to figure out how to fit this aircraft, which ideally is on the ground already backing the flow for yet another approach."

I Need to Know as Soon as Possible(0:37)

Brandon MillerRadar ControllerUnited States

"As a radar controller I need to know as soon as possible if I've asked you to do something that's unmanageable to you. I need to know if you're too high, too fast and I need to know as soon as I can, so that I can formulate a new plan to ensure that my sequence works for everybody behind you and everybody in front of you. I need to know if I've asked you to do something that the aircraft can't do, you as a pilot can't do or you're uncomfortable with doing, so that I can plan for everybody in front of you and behind you and set a new sequence if necessary."

Ensure That the Runway is Clear(0:25)

Connie ThompsonTower ControllerUnited States

"As an air traffic controller my primary duty is to ensure the safety of each airplane I talk with. Providing the most up-to-date weather information, ensuring that that runway is completely clear for that pilot. And not putting a pilot in a situation which may be uncomfortable for both he and the passengers."

Early Planning(0:48)

Captain Ted PakiiChief Executive OfficerPapua New Guinea

"Early planning for all approaching arrivals, issue your instructions accordingly. Issue the decent and approach instructions at lease 20 to 30 minutes prior to top of decent so that the pilots will get the associate time to program their computers. Avoid deviation from the pre-cleared clearances for flight profiles and if there is a real need for it minimize it, make it nice and small. After the pilot is on the track miles if you are vectoring them use radar vectors. Once STAR is commenced avoid deviating from those as much as possible at the same time."

Reduce the Risk of Runway Excursions(1:58)

Stephen AngusExecutive General ManagerAustralia

"Unstable approaches leading to a runway excursion continues to be one of the global risks for aviation. With increasing traffic growth globally, new airports, we must do everything we can to improve runway safety. You've heard from global safety experts from every part of the world who've worked together to produce a whole toolkit to reduce runway excursions from unstable approaches. The toolkit and guidance that you have been provided with is truly a global cross industry participation activity. With airports, airlines, the regulators and service providers contributing together to provide this guidance. Every person and organization that works in and around an airport can make a major safety contribution to reduce the risk of a runway incident. CANSO has come together with these partners to produce this toolkit and guidance. There is material here for pilots, airlines, air traffic controllers, regulators, and airport owners who all can take this material and reduce the risk of a runway excursion. Unstable approaches is a major contribution to this safety issue and we encourage everyone to take this material and start to use it within their organization. I'm so pleased to announce this material and to encourage all of this collaboration now to become a fruitful exercise in safety reduction. The runway safety maturity checklist is one of the most important parts of this guidance material. It provides the right material for all partners and all stakeholders within the airport to develop local plans to reduce the risk of a runway excursion."

CANSO is the global voice of the companies that provide air traffic control, and represents the interests of Air Navigation Service Providers worldwide. CANSO Members are responsible for supporting 85% of world air traffic, and through our Workgroups, Members share information and develop new policies, with the ultimate aim of improving navigation in the air and on the ground. CANSO also represents its members' views in major regulatory and industry forums, including at ICAO, where we have official Observer status.